8T vs. 6T SRAM cell radiation robustness: A comparative analysis

We analyze and compare the impact of radiation-induced transient effects based on evaluating the critical charge parameter for 6T and 8T SRAMs during hold, read and write operations. Results on a commercial 65 nm CMOS technology show that 6T and 8T cells offer quite similar robustness when they are in hold. However, the critical charge observed in other operation modes is reduced a 55% respect to the hold operation. For this reason, we provide a thorough analysis of the critical charge behavior in 6T and 8T SRAMs to determine the dependence of memory radiation robustness with memory state. Single event upsets and single event transients have been considered in the analysis, showing that 8T have better performance than 6T. The dependence of critical charge with memory state for high workload memories modifies the overall memory SER estimation indicating the significance of analyzing the memory robustness as a memory state function. In general, the SER estimation results show that the robustness behavior of 8T-based cells is better than robustness behavior of 6T-based cells.